pH-assisted homogeneous liquid-liquid microextraction using dialkylphosphoric acid as an extraction solvent for the determination of chlorophenols in water samples

Tailoring supramolecular solvents with phosphoryl groups for highly efficient extraction of chlorophenols in natural waters

BACKGROUND

Chlorophenols are routinely determined in aquatic systems to check compliance with the restrictive international legislations set for protection of human and aquatic life. Their control requires affordable analytical methods, particularly in labs at low- and medium-income countries. Liquid chromatography-UV detection is a convenient technique for this purpose, but the availability of suitable sample processing remains pending. Organic solvents are inefficient for extracting the whole range of chlorophenols whereas solid-phase extractions are expensive and labour-intensive. So, an efficient, fast and cheap extraction of chlorophenols, amenable to any lab, would help to cope with their worldwide analytical control in natural waters.

RESULTS

A supramolecular solvent (SUPRAS) was tailored for providing mixed interaction mechanisms aimed at the efficient extraction of chlorophenols prior to LC-UV. The SUPRAS was synthesized from the self-assembly of hexylphosphonic acid under acidic conditions and consisted of sponge-like nanostructures made up of amphiphile and water. The phosphoryl (PO) group was selected as the major driver of the extraction because of its ability to act as halogen and hydrogen bond acceptor for chlorophenols. Additional interactions were hydrogen bonds from O-H amphiphilic groups and the surrounding water, and dispersion and CH-π interactions in the hydrocarbon chains. The number of binding sites in the SUPRAS could be modulated by addition of salt. The SUPRAS formed in situ in the sample, the extraction took 5 min, the concentration factor was around 220, quantification limits (0.1-0.3 μg L-1) were below the EU standards, and the method worked for natural waters.

SIGNIFICANCE

A fast, low-cost, and organic solvent-free sample processing only requiring conventional lab equipment (stirrers and centrifuges) provided SUPRAS extracts that could be directly analyzed by LC-UV. SUPRAS synthesis occurred spontaneously in the water sample under addition of hexylphosphonic acid and the whole process required low skills. The method meets the analytical and operational performances for the analytical control of chlorophenols in natural waters and it is within the reach of any lab.

Homogeneous liquid-liquid extraction as an alternative sample preparation technique for biomedical analysis

Liquid-liquid extraction is a widely used technique of sample preparation in biomedical analysis. In spite of the high pre-concentration capacities of liquid-liquid extraction, it suffers from a number of limitations including time and effort consumption, large organic solvent utilization, and poor performance in highly polar analytes. Homogeneous liquid-liquid extraction is an alternative sample preparation technique that overcomes some drawbacks of conventional liquid-liquid extraction, and allows employing greener organic solvents in sample treatment. In homogeneous liquid-liquid extraction, a homogeneous phase is formed between the aqueous sample and the water-miscible extractant, followed by chemically or physically induced phase separation. To form the homogeneous phase, aqueous samples are mixed with water-miscible organic solvents, water-immiscible solvents/cosolvents, surfactants, or smart polymers. Then, phase separation is induced chemically (adding salt, sugar, or buffer) or physically (changing temperature or pH). This mode is rapid, sustainable, and cost-effective in comparison with other sample preparation techniques. Moreover, homogeneous liquid-liquid extraction is more suitable for the extraction of delicate macromolecules such as enzymes, hormones, and proteins and it is more compatible with liquid chromatography with tandem mass spectrometry, which is a vital technique in metabolomics and proteomics. In this review, the principle, types, applications, automation, and technical aspects of homogeneous liquid-liquid extraction are discussed.

Ultrasound-assisted extraction combined with reverse phase-dispersive liquid-liquid micro extraction as a new approach for preconcentration and spectrophotometric determination of total phenol in marine sediments of Chabahar Bay

In this study, Reverse phase dispersive liquid-liquid micro extraction (RP-DLLME) technique have been successfully developed to preconcentrate trace amount of phenol from sediment samples as a prior step to its derivatization with 4-aminoantipyrine and enhanced determination by UV-Vis spectrophotometry after primary ultrasonic extraction. In this procedure, 50μL 0.7M NaOH solution was chosen as extraction solvent and other factors including pH, extraction time, concentration of 4-aminoantipyrine, type and volume of dispersive solvents were optimized. Under selected conditions, the limit of detection, the linearity range, relative standard deviation and enrichment factor of method were obtained 15μg·kg(-1), 50-1800μg·kg(-1), 4.8% (n=10) and 33, respectively. Finally, using the high sensitivity, low organic solvent consumption and waste generation method, total phenol content in marine sediments from several locations in Chabahar Bay (southeast Iran) was estimated at 55.8-73.2μg·kg(-1).

Reversed-phase vortex-assisted liquid-liquid microextraction: a new sample preparation method for the determination of amygdalin in oil and kernel samples

A novel, simple, and rapid reversed-phase vortex-assisted liquid-liquid microextraction coupled with high-performance liquid chromatography has been introduced for the extraction, clean-up, and preconcentration of amygdalin in oil and kernel samples. In this technique, deionized water was used as the extracting solvent. Unlike the reversed-phase dispersive liquid-liquid microextraction, dispersive solvent was eliminated in the proposed method. Various parameters that affected the extraction efficiency, such as extracting solvent volume and its pH, vortex, and centrifuging times were evaluated and optimized. The calibration curve shows good linearity (r(2) = 0.9955) and precision (RSD < 5.2%) in the range of 0.07-20 μg/mL. The limit of detection and limit of quantitation were 0.02 and 0.07 μg/mL, respectively. The recoveries were in the range of 96.0-102.0% with relative standard deviation values ranging from 4.0 to 5.1%. Unlike the conventional extraction methods for plant extracts, no evaporative and re-solubilizing operations were needed in the proposed technique.